What is Gene Therapy? - Definition, History Pros, Cons & Examples

Instructor: Hilary North

Hilary is a biomedical researcher with a PhD in neuroscience.

Learn how gene therapy is used to treat disease, the history of the treatment and its trials, as well as the pros and cons associated with this controversial new technique.

Proteins and Disease

Gene therapy is a therapeutic technique that replaces damaged proteins by inserting the DNA for that protein into a cell. What is the significance of replacing damaged proteins, and how is this accomplished?

Proteins are responsible for a multitude of cellular functions that are crucial to the survival of cells and the organs they populate. Proteins are produced through a process known as protein synthesis. During protein synthesis, a protein is built based upon the blueprint, or code, that outlines its structure. This code is found in the genes, also known as DNA. Many diseases are caused by improper protein production, when either too much or too little of a certain protein is produced or a defect in the production process occurs, it leads to a protein being formed incorrectly.

How Does Gene Therapy Work?

Gene therapy replaces proteins in the cell by artificially introducing the DNA code into the cell. It is different from other forms of medicine that might introduce a chemical or protein into cells but not DNA. If the precise code for making the protein that is needed to treat a disease is known, doctors can synthesize a strand of DNA in a test tube and then deliver it into the patient's cells.

There are a number of DNA-delivery techniques possible. One common approach is to insert the artificial DNA into an un-harmful virus, which naturally inserts DNA into host cells, and inject the patient with the virus. The virus will deposit the artificial DNA into the patient's cells, and the existing cellular machinery engages in protein synthesis by reading the artificial DNA code and producing the desired protein.

Gene Therapy Cons

The concept of gene therapy is creative, unique and promising. But it is technically challenging and has a number of hurdles to clear:

  • Gene therapy is not possible when the genetic code for a protein has not been discovered.
  • The DNA introduced by gene therapy will be degraded naturally inside the cell; therefore, the treatment will be transient.
  • The patient's immune system will recognize the DNA introduced by gene therapy as a foreign pathogen and attack it, a reaction that may either damage the DNA and prevent it from succeeding therapeutically or harm the patient.
  • Gene therapy remains prohibitively expensive. For instance, there is a gene therapy drug on the market that costs around $1,600,000 per patient- the most expensive drug in the world!

Gene Therapy Pros

Despite these hurdles, the promise of gene therapy is worth the investment:

  • Gene therapy makes production of a dysfunctional protein inside a cell possible.
  • Gene therapy can theoretically be tailored to replace any protein imaginable, making it useful for a huge number of diseases.

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